LOS ANGELES — Pregnancies complicated by type 1 or type 2 diabetes mellitus can have good outcomes with new strategies for glucose control, Steven G. Gabbe, M.D., said at the annual meeting of the Society for Gynecologic Investigation.
At less than 5%, the perinatal mortality rate of children whose mothers have diabetes is comparable with the rate in children of women without diabetes, according to Dr. Gabbe, dean of Vanderbilt University School of Medicine in Nashville, Tenn. Nonetheless, preventing congenital malformations and overly large babies remains a challenge.
“We have to develop individualized programs of insulin for our patients,” he said, outlining strategies that emphasize patient education and self-management.
Glucose control goals change with pregnancy, Dr. Gabbe said. Physicians should counsel diabetic women before conception to bring their glycosylated hemoglobin (HbA1c) levels to no more than 1% above the normal range. Targeted plasma glucose levels should be 80–110 mg/dL before meals and less than 155 mg/dL after meals.
During pregnancy, target plasma glucose levels should be 60–90 mg/dL before breakfast; 60–105 mg/dL before lunch, supper, or a bedtime snack; less than 120 mg/dL 2 hours after meals; and above 60 mg/dL between 2 a.m. and 6 a.m. The mean capillary glucose level should be maintained below 100 mg/dL.
To help patients use HbA1c levels to approximate mean glucose levels, he suggested teaching them “the rule of eights”: An HbA1c of 8% equals 180 mg/dL, and each 1% change equals ±30 mg/dL.
Pregnant patients need to understand that there is a “lag time” between an injection of insulin and a meal (N. Engl. J. Med. 2005;352:174–83), he continued. Physicians should also warn them against “insulin stacking” in which a correction dose of insulin is given before the prior dose of prandial insulin has reached its peak effect (JAMA 2003;289:2254–64).
Insulin stacking leads to hypoglycemia, he warned. “You have to remember and remind patients about overcorrecting with too much insulin too soon before the insulin they have taken has played out.”
Dr. Gabbe said insulin levels increase during pregnancy, but the changes are different for each woman. To help the patient make adjustments, he recommended teaching her that:
▸ One unit of short-acting insulin will lower her blood glucose level by about 30 mg/dL.
▸ Ten grams of carbohydrate will elevate her blood glucose by about 30 mg/dL.
▸ One unit of short-acting insulin will cover about 10 g of carbohydrates.
He recommended the short-acting insulins lispro and aspart for pregnant patients; these can be injected or used with an insulin pump. He said there are concerns but not much experience with the long-acting insulin glargine in pregnancy.
Insulin pumps offer many advantages, he said. Along with eliminating the need for multiple injections, they provide a continuous basal rate, which reduces the risk of mean glucose excursions and hypoglycemia. Patients generally like the pump, because it allows a more flexible lifestyle.
The pumps have disadvantages, however. He said pumps require excellent patient compliance, along with intensive glucose monitoring, and can produce hypo- or hyperglycemia if mechanical problems occur. Pump failure increases the potential for ketoacidosis, and there is the potential for infection at the insertion site.
Expense is another issue. “It costs $140 more per month to use a pump vs. multiple injections,” he said.
Whatever method is used, Dr. Gabbe said diet is critical as well. Patients should have three meals and three snacks each day.
Another concern is hypoglycemia unawareness, which he warned could be exacerbated by intensive insulin therapy during pregnancy. Determine whether the patient has hypoglycemia unawareness; review and adjust her diet, insulin, and exercise; and teach family members to treat hypoglycemia, Dr. Gabbe said.
“Does all of this really make a difference?” he asked rhetorically. “Yes, it does—in having a baby that grows normally and behaves normally in the nursery.”